Paleoclimatic reconstruction of northwest Himalaya since CE 475 using lake sediments from Tadag Taal, Kumaun, India

The Kumaun region of India in the northwestern Himalaya experiences complex rainfall patterns, receiving precipitation both during the summer monsoon (June to September) as well as during winter months dominated by westerlies (October to March). In this paper, we present a multi-proxy palaeoclimate record spanning the last ∼1500 years from Tadag Taal, an intermontane lake in Kumaun, India. Our dataset (stable isotope ratios, grain size, trace element ratios) suggests the occurrence of four long-term precipitation cycles of high and low rainfall coinciding with the Dark Ages Cold Period (DACP, ∼475–850 CE), Medieval Climate Anomaly (MCA ∼900–1300 CE), Little Ice Age (LIA, ∼1450–1800 CE) and Current Warm Period (CWP, ∼1850 CE to Present). We infer multi-decadal to centennial-scale shifts in the Indian summer monsoon co-varying with changes in El Niño-Southern Oscillation (ENSO) activity superimposed by changes in solar insolation. To correlate our time-series from the northwestern Himalaya with the Core Monsoon Zone and understand coherency in precipitation between the two regions, we applied the Wavelength Coherency Test. Our data suggest wet conditions during the early phase of the LIA (∼1450–1640 CE) and dry conditions in the later phase of the LIA from ∼1640–1800 CE. The wet conditions in the early LIA were perhaps driven by increased winter precipitation. This is in contrast to Central India that witnessed dry conditions during the entire duration of the LIA. This study thus suggests that monsoon strength was different during earlier and later phase of the LIA. Further, the LIA did not witness uniform climate variability through its duration as has been reported in some European and Chinese proxy records.